A tactical move or series of moves based on the opponent’s weakened King, hanging or undefended pieces or inadequately guarded pieces. Usually involving a sacrifice, it is a calculable series of moves leading to material or positional gains. It is important to note that a combination cannot exist if at least one of the above factors is not present. Though several players have attempted to create a clear definition throughout the years, the following definition by Silman and Seirawan is the most accurate: A combination is a sacrifice, combined with a forced sequence of moves, that exploits specific peculiarities of the position in the hope of attaining a certain goal.
A sequence of moves involving a SACRIFICE played in order to gain a specific advantage, usually to win MATERIAL or to force CHECKMATE, sometimes to force a draw from an inferior position.